Off the ball incident - Ferdinand/Torres

Why didn't Rio get a red card for that off the ball 'assault' on Torres?

Was it because Howard Webb had his selective Man United favouring vision in play again?

Rio's behaviour is disgusting, berating a referee after the defeat against Real Madrid and now kicking another player to the floor in an off the ball incident and getting away with it, all because Chelsea had pulled themselves back level...

True, it was a straightforward stupid thing to do, especially as Chelsea's incarnation of Torres is not exactly someone we need to be scared of. I can only assume Webb didn't see it, as it was so far off the ball, otherwise, Rio would be incredibly lucky if he only got booked for that.